Flame shapes were measured for buoyant and nonbuoyant laminar gas jet diffusion flames burning, methane, ethane, and propane in quiescent air. Test conditions involved burner diameters of 0.19-5.5 mm, ambient pressures of 0.25-2 atm, and fuel flowrates of 0.04-4.6 mg/s. Care was taken to minimize interference from soot emissions and from ignition disturbances. Microgravity conditions were obtained in the 2.2-s drop tower at the NASA Lewis Research Center. Normalized lengths of both buoyant and nonbuoyant flames were proportional to source Reynolds number, but the nonbuoyant flames were 40% longer on average. Normalized widths of the nonbuoyant flames were constant for Re greater than or equal to 100, whereas buoyant flame widths scaled with source Froude number. Several nonbuoyant flame models are evaluated with the present shape data. (C) 1998 by The Combustion Institute.